Frost bank automatic defrost actuator



1956 R. w. WOOD, JR

FROST BANK AUTOMATIC DEFROST ACTUATOR Filed July 16, 53

2 Sheets-Sheet United States Patent Ofice 2376755 5 FROST BANK AUTOMATIC DEFROST ACTUATOR Rountree Wicklife Wood, Jr., Evansvlle, Ind., assigno', by mesne assignments, to Whirlpool-Seeger Corporalion, a co'poration of Delaware Application July 16, 1958, 'Serial No. 368,274 7 Claims. (Cl. 62-2) trolling such operation.

It is a principal object of this invention to provide an improved mechanisn for intiating the defrost cycle manual manipulation A yet still further of the control device. object is to provide an improved erence may be had to which:

10 fashioned with an outer shell or wall 11, an inner evaporator 13, a door 14 hingedly mounted on one side of said evaporator, and a cabnet 2,767,555 Patented Oct. 23, 1956 closure or door 15 suitably hinged on one side wall of the cabinet.

or bracket-like support member 19 having upturned 20 and 21, respectively, along opposite marginal `.dges thereof, and with an opening 22 in the base thereof. A pair of parailel 'ods or plungers 23 and 24 are spaced a collar 33, positioned by the pin 34, serves to maintain said spring normally compressed and disposed in abutting relation with the flange 21.

A generally L-shaped Operating or actuating lever 35 as one edge thereof upturned to provide a flange 36 which, preferably, is curved or rounded at one end as shown at 37 for end of a headed pin or stud 42 the opposite end of 24, while a retaining and cotter pin 44 function to secure said lever to said rod in a combined slidng and rotatable relationship.

As best seen in Figure 5 frost-engaging channel member 45 that is affixed, by some suitable means such as the welding indicated at 46, to the rod 23 and is adapted to slide therewith. One leg of said and into the space adjoinin but actual contact therewith the surface thereof. The spacng provided between the ends of this channel and the evaporator depends upon the amount of frost it is desired be accumulated before the various Components of. the

device becomes operative to initiate the defrost cycle and hence the dimension or thickness of the shims 18 may be selected accordingly. The opening 22 in said base should be of such dimension as to preclude binding or frictional engagement between said channel member and the walls of the opening as said member slides along through the opening with each operation of the rod or plunger 23, as well as to provide a space in which the frost' may accumulate or build-up around said frostengaging member. The fianged edge 36 of the Operating lever 35 is adapted to contact a plunger 48, which forms part of the Operating mechanism of a defrost heat control electrical circuit switch 41 likewise mounted by suitable means on the base 19, and as said actuating lever rotates about its pivotal stud 38 said fiange will slide along the Contacting surface of said plunger until the curved extension 37 thereof eventually picks up the contact and maintains it throughout the remainder of the movement of said lever.

As shown in the schematic representation depicted in Fig. 6 the refrigeration system includes a motorcompressor unit 50 which is connected to a suitable 'source of electrical power through a conventional temperature control device 51 and through the defrost heat control switch 49. The detrost heating means, indicated generally by the reference character 52, may include any well known electrical resistance coils or units which are attached by suitable means to the refrigerart evaporator 13 and arranged so that When the coils or unts are energized the heat therefrom will ettectively melt the frost 'from said evaporator.

The defrost heat control electrical circuit switch 49 may be any suitable switch adapted for opening one electrical circuit and then closing a second circuit, and further having means associated therewith for restorng initial conditions by reversing the operation at a subsequent time as a result of a temperature variation in a portion of the referigeration system. This device lS ashoned generally as a single pole double throw switch in' which a switch arm 53 may be snapped into one of `two positions by means of the plunger 48. In one such position the arm 53- engages the contact 54 and completes the electri-'cal circuit through the motor-compressor unit 50, and in the other position it engages the contact 55 and energizes the electrical circuit through the. defrost heating device 52. The arm 53 is, provided with well known snap-spring means (not shown) which enables it to be snapped from one position to the other and retained in such position until otherwise released. This switch is further provided with a temperature control mechanism which actuates said switch to interrupt the electrical circuit through the defrost heating means in response to.` a preselected temperature in the eva-porator. This is" accornplished by an actuating lever 56 that is arranged to operate the arm 53 and break the circuit through contact 55 as a result of a motivating force suppliedbythe operation of a sylphon bellows 57', in turn 'connected by a, capillary tube 58 to a feeler bulb 59 suitably mounted, preferably, proximate the coldest spo On, the evaporator 13. The feeler bulb, capillary nd bellows are, of course, provided with a volatileifiuid that; eirpands, and contracts in response to temperature changes as is well understood in the art. While any pre-selected temperature setting desired may be used it has: been found that a temperature setting; of; the order of; 4,7 degrees (plus o-r minusZ degrees) Fahrenheit is highly effective in restoring the switch to normal at the best time.

To explain the' operation of the proposed invention it is assumed that the evaporator door 14. is closed, as

shown` in Fig; 2, whereupon the relative position of the control mechanism will be substantially as indicated in Fig. 3. ln this instance .the

evaporator door will abut or engage both bumpers 25 and 30while their respective rods 23 and 2.4will be slidably positioned rearwardly both rods being moved lows 57 will have an equal distance, and the corresponding springs 27 and 32 will be somewhat compressed. The Operating or actuating lever 35 at this time will be positioned substantially normal to the rods 23 and 24 and the channel member 45 will be disposed proximate one end of the opening 22 in the base member 19. When the evaporator door is opened, as indicated in Fig. l, the bumpers 25 and 30 are free to move and, aided by the actions of their respective springs 27 and 32, will be propelled forwardly an equal distance carrying with them the Operating lever 35 and the channel member The parts of the mecha nism may be so dimensioned that when the channel member 45 reaches the front of the opening 22 the springs 27 and 32 will be extended to their unloaded positions, but, if not, the stops 26 and 31 on the rods will abut the fiange 21 and prohibit or restrict further forward movement thereof.

As is well known in the art with each opening of the cabinet door 15 there is a build-up of a limited amount of fro'st upon the exterior surfaces of the evaporator until finally the deposit thereon is sufficiently thick as to re quire removal in any suitable manner. In the proposed device when the frost builds up to a predetermined thickness on the evaporator it Contacts the flange 47, of the frost-engaging channel member 45, and eventually surrounds this flange and a portion of the opposite leg` of said channel member. At this time the opening 22 will also be so filled with frost that said channel member becomes locked or frozen in place, thereby prohibiting any sliding motion of said member, or of the rod 23 to which it is atfixed, and when such conditions prevail the evaporator is ready for defrosting.

Under such conditions when the evaporator door 14 is next opened the bumper 30 being free to move will be propelled forwardly by the action of spring 32 but bumper 25 must remain in position because of the ice-locked condition of the channel member 45 with which it is associated. The relative position of the various parts of the mechanism under this condition is best shown in Fig. 4. As the rod' 24 slides forwardly, upon opening of the evaporator door, it carries with it one end of the operating lever 35 and, while another portion of said lever rotates about the pivotal stud 38 in the rod 23, the pin or stud 42 freely slides in the slotted opening 41 in said lever and thus does not interfere with the sliding motion of the rod 24'. The actuating lever 35 after being thus rotated will be positioned so that the flange 36 on the opposite end thereof depresses the plunger 48, of the defrost heat control switch 49, and thereby initiates the operation of the defrost cycle. When the temperature of the evaporator 13 is such that it 'requires defrosting the bellows 57, of the thermostatic device associated with said switch, will be. contracted sufficiently to permit the plunger 48 when depressed to snap the switch arm 53 out of engage ment with contact 54 and into engagementwith contact 55. When the circuit through contact 54 is broken the motor-compressor unit 50 will cease to operate, andwhen the circuit through contact 55 is' energized the defrost heater unit 52 will begin to heat and melt the frost from the evaporator. The thermostatic device, of which the bellows 57 forms a part, being adjusted for a particular temperature when the evaporator reaches this predeter mined value the bellows 57 expands and actuates. the lever 56 thereby interrupting the flow of electrical current through the defrost heater unit 52, and' reenergizing the circuit through the motor-compressor unit 50.to return the refrigeration system to normalcyclingwith the temperature control unit `51 controlling future cycling thereof. As soon as the temperature ofpthe evaporator is again reduced, through normal, Cycling of the system, the belcontracted and moved away from the lever sfadistance suicient to permit theplunger& to freely snap the switch arm 53 again when thedefrost cycle issubsequently initiated. Iftheplunger 48 should be' m nually` epressed before. the temperature of" the What is claimed is:

1. In a refrigerator including an evaporator, evaporator defrosting means and said evaporator; and second members slidably mounted on said bracket; an actuatng arm pivotally aflixed to the said first member and slidably afixed to the said second member, and having an end portion of said arm disposed adjacent said switch; resilient means reactive on said first members for urging said actuatng arm out ment with said switch; said arm being manually rotatable into position such that the end portion thereof engages said switch and initiates operation of said defrosting means. V

2. In a refrigerator including an evaporator, evaporator defrosting means and means for controlling said evaporator defrosting means comprsing: a bracket mounted on said evaporator; a switch carried by said bracket; first and second members disposed parallel to one another with each being slidably mounted in said bracket; an actuatng arm pivotally affixed intermediate the ends thereof to said first member, and slidably secured proximate one end thereof to said second member, and having the opposite end thereof adapted for engaging said switch; resilient means reactve on said first and second members for urging said actuatng arm normally out of engagement with said switch; said actuatng arm being arranged to rotate into engagement with said switch and initiate operation of said defrosting means upon application of force to one end of said first member.

3. In a refrigerator having an evaporator, evaporator defrosting means and a door, means for controlling said evaporator defrosting means comprising: a bracket mounted on said evaporator; a switch carried by said bracket; first and second member slidably mounted in said bracket and having one end of each member disposed adjacent the door in its closed position; an actuatng arm pivotally secured to each of said members and having one end thereof disposed adjacent said switch; a frost-engaging member afiixed to said first member and disposed so that said first member is constrained against movement When a predetermined thickness of frost accumulates on the evaporator adjacent said frost-engaging member; reslient means urging said first and second members into engagement with said door when closed so that upon opening said door when the frost is of a predetermined thickness the said second member will slide axially to rotate said actuatng arm into engagement with said switch to initiate operation of said defrosting means.

4. In a refrigerator having an evaporator, evaporator defrosting means and a door, means for actuatng said evaporator defrosting means comprising: a support bracket having an opening therein and mounted on said evaporator; a switch carried by said support bracket; first and second members slidably mounted in said support bracket, and having one end of each member disposed adjacent the door in its closed position; an actuatng arm pivotally secured to each of said members, and having one end thereof disposed adjacent said switch; a frost-engaging member afiixed to 'said first member and projecting through said support bracket rotate said actuatng arm into engagement with said switch to initiate operation of said defrosting means.

5. In a refrigerator, having an evaporator, evaporator door and evaporator defrost'ng means, means for conevaporator in spaced relaton therefrom; a by said bracket; first and second members slidably mounted in said bracket, and having one end of each adjacent said evaporator door in its and having one end of said arm disposed adjacent said switch; a frost-engaging member depending from said first member and projecting through members, and having one end thereof disposed adjacent said switch; a frost-engaging member depending from said first member and projectng through said bracket opening into the space between said evaporator and said bracket so that when a quantity of frost accumulates on said frost-engaging member and fixedly positions said member the said first member is constrained and resilient means urging said second member will slide axially to rotate said actuating arm into engagement with said switch to initiate operation of said defrosting means.

7. In a refrigerator, including an evaporator, evaporator defrosting means and a door, means for initating parallelly disposed and slidably mounted in said bracket, and having one end of its closed position; arm pivotally secured to said first member; means slidably securing said actuatng arm to said second member including a slotted opening proximate one end of said actuating arm and a pivotal stud that passes through said slotted opening and is carried by said second member; a frost-engaging member depending from said first member and projecting through said bracket opening and into one end of said arm to engage said switch and initiate the space between said evaporator and said backet so operation oi said` defrosting means\ V that whea,predetermned` quantity Offl'OS'L bridges the V i spacebetween said frostengaging member andthe evaposc e i the f h patent pato! said ffiost-engaging member is fixedly positioned UNITED STATES PATENTS andsaclfirst member from which it dependsis constrained against movement; resilient means urgng said first and 4 9 Schwetzer July 1935 second members into. engagement with said` door in its 22064910. Huu 1936 closed position so that upon the opening thereof the 2,147867 lpin Feb. 21, 1939 pivotal; stud in said second member is: slidable inthe 10 23 3 9 Marcy May 15, 1945 slotted opening of. said actuatng` arm for rotating; said 2,62 Grimshaw Jan. 6, 1953 arm. about its pivot in said first member and causing 2,704,441 Morton 23, 1955 

